WO 2006/043115 discloses a cost-effective analog mechanism that enables flexibility in the routing of channels between uplink and downlink beams, wherein all uplink channels from a variety of microwave bands are converted to a first intermediate frequency (“IF”), and agile filters are employed to filter and translate selected channels to a second IF, in order to group the selected channels together for transmission on a downlink beam.
WO 2006/085116 and U.S. Pat. No. 4,262,361 disclose a form of agile filter having a continuously variable bandwidth which includes a local oscillator and mixers for adjusting the position of an input signal relative to bandpass filter edges. A problem with the techniques disclosed in the above documents is that where a large number of agile filters is required for channel routing, this introduces a great amount of phase noise.